1. Field of the Invention
The present invention relates to an improvement in the fixed bed reactors which are commonly used in fundamental chemical processes. More particularly, the invention relates to a membrane catalytic reactor in which the reaction and separation are carried out simultaneously in a single step resulting in an improvement in reaction productivity and separation efficiency.
2. Description of the Prior Art
In conventional chemical processes using a fixed bed reactor, a reaction and a separation steps are independently carried out. Generally, it is essential to carry out the separation step in order to recover the final product formed from the reaction in desired purity.
In general, most chemical reactions occur at a high temperature over 300.degree. C. At such an elevated temperature, polymeric separation membranes exhibit thermal instability; thus, few polymeric separation membranes have been used for membrane catalytic reactors. Consequently, nowadays, studies on inorganic membranes which can endure high temperatures have extensively been performed.
For example, Uemiya, et al. used a palladium catalyst membrane reactor in the aromatization of propane; see Chemistry Letters, pp. 1335-1338 (1990). Uemiya, et al. also used a hydrogen-permeable membrane in the steam reforming of methane; see Applied Catalysis, 67, pp. 223-230 (1991).
However, the separation mechanism of these inorganic membranes generally exhibits characteristics depending on their pore sizes and, thus, the mechanism is simpler than that of polymeric separation membranes. Therefore, the inorganic membrane cannot afford a variety of characteristics of separating materials.
Polymeric separation membranes have low thermal stability. However, the separation mechanism of these membranes varies with the diffusibility and the solubility of the relevant material; thus, they can have good separation abilities for a variety of materials in chemical reactions at low temperatures.